ValidParentheses.js

/*
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', 
determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.

*/

const isValidParentheses = function (s) {
  const map = {
    "(": ")",
    "{": "}",
    "[": "]",
  };
  let stack = [];

  for (let i = 0; i < s.length; i++) {
    if (s[i] === "(" || s[i] === "{" || s[i] === "[") {
      stack.push(s[i]);
    } else {
      if (map[stack.pop()] !== s[i]) return false;
    }
  } 
  return stack.length ? false : true;
};

console.log(isValidParentheses("()"));
console.log(isValidParentheses("({[}])"));
console.log(isValidParentheses("(]"));
console.log(isValidParentheses("([)]"));
console.log(isValidParentheses("{[]}"));
console.log(isValidParentheses("(("));